Research On Temperature Field Analysis And Thermal Compensation Sealing Device Of Rotary Air Preheater

The amount of thermal power generation accounts for 74.16% of China's total power generation.The rotary air preheater is widely used in thermal power plant boilers due to its compact structure and high heat exchange efficiency,however,due to the structure of the air preheater and the high temperature difference,its air leakage rate has increased by more than 10% from 3%~5%.The Electric Power Academy data shows: the air leakage rate will decrease by 1%,and 5000 hours will save 4,620 tons of standard coal for one 600 MW unit.Therefore,reducing the air leakage rate of the air preheater not only has a positive effect on the prevention and control of environmental pollution,but also has significant effects on resource conservation and cost reduction.This paper analyzes the structure of rotary air preheater,summarizes the research status of air leakage in air preheater and the research status of sealing device.It is determined that the air leakage of air preheater is mainly due to the large temperature difference between the two ends of the rotor(more than 250 °C),and the occurrence of "mushroom" heat the deformation causes the radial gap of the hot end to become larger,and the air leakage rate suddenly increases.Therefore,a composite flexible sealing device composed of a combination of a flexible sealing blade and a heat-compensating metal structure is introduced,which can adaptively seal the hot-end radial air leakage gap.Taking a 600 MW rotary air preheater in Fuyang as an example,the temperature distribution and deformation of the air preheater rotor are studied through theoretical and simulation.The existing mathematical model research is analyzed to summarize the mathematical model of the air preheater rotor temperature;the air preheater fluid thermal simulation model was established to simulate rotor temperature distribution and thermal deformation.The simulation results verify that the mathematical model error is 18.4% and the empirical formula error is 4.9%.The working principle of the flexible sealing blade and the sealing device is briefly analyzed,and the thermal compensation metal structure is mainly studied.Through theoretical calculation and simulation analysis,a thermal compensation metal structure suitable for deformation of 5mm~39.7mm is obtained.At the same time,the influence of thermal bimetal parameters(length,width and thickness)on the deformation of thermal compensation metal structure is studied,which provides theoretical guidance for the serialization and standardization of composite flexible sealing devices.it also provides a new idea for structural design in medium and high temperature environments.Considering the temperature effect,the safety of the Fuyang 600 MW air preheater sector plate and axial sealing plate under hoisting and 400°C working environment was studied.The finite element model of the sector plate and the axial sealing plate is established.The thermal field analysis shows that the safety factor of the axial sealing plate is 15.7 in the operating state and the safety factor of the hot-end sector plate is 1.39.